We intend to prepare novel nucleotides which are designed to be inhibitors of certain enzymes of purine nucleotide biosynthesis. These inhibitors are transition-state or multisubstrate analogs of the reactions catalyzed by the target enzymes. The initial enzyme targets selected are IMP dehydrogenase and GMP Synthetase. The compounds will be evaluated as inhibitors of the target enzymes before any additional testing will be planned. The compounds will have two potentially important uses: a) as probes for studies on the catalytic mechanisms of the target enzymes, and b) as potential anticancer drugs.